Personally I wouldn't put either of the triggers in there as I think it's a bit too small.
I love lionfish though. I personally would have a few dwarf fuzzy lions or maybe 1 Radiata lion (pterois radiata) with possibly a sailfin scorpionfish (amblyapistus taenionotus) or if you wanted some more colour a Valentini Puffer (canthigaster valentini)
I'd maybe consider a snowflake eel (echidna nebulosa)